D600 shutter lag

I've noticed that my D600 has developed a shutter lag in firing with my SB-900 attached with either a SC-29 or directly to the camera's hot shoe. When I am using the camera with the SB-29/SB-900/SG-9 and the D600 will not fire once the shutter button is lightly touched. I have to mash down and hold it down then it fires but the frame rate is really slow. Unhook the SC-29 from the camera and the shutter button is back to normal. Reattach the SC-29 and its lag time again.
I have tried my D3 in this situation with the same SB-29/SB-900/SG-9 and the response is instant.
I have replaced the batteries in the SG-9 and SB-900. The battery is charged in the D600. I've checked the camera menus and nothing is out of order.
I am shooting in deep shade and sunlight. The problem occurs in either situation.
However last year with this D600/SB-29/SG-9/300mm/800mm rig worked instantly and at a higher frame rate. The above paragraph happened the other day.
I've used this same rig in May at Magee Marsh for 4 weeks and it worked perfectly. Is my shutter button getting old and needs to be replaced by Nikon?
Thanks for any light that you folks may shed on this.

Larry Shuman

It likely means you have got red-eye reduction turned on.

I have checked both the manual and camera and I do not see any indication of red eye reduction being on. On the top LCD it shows shutter and aperture , matrix mode, focus mode, WB, auto-ISO, single sensor and sd cards. I do not see the symbol for red eye reduction. The only thing I see is the strobe symbol on the left side of the LCD when a strobe is turned on. The symbol will leave the LCD when I remove the strobe from the hot shoe. Will a 2 button reset fix the problem?
Two weeks ago the camera/flash worked perfectly and delivered a 24x36 of a Pine Siskin.

On the top LCD, do you see both the lightning bolt and the picture of an eye? if so Red-eye reduction is on. That is usually what causes the delay. See page 144 of your manual.

The other thing that can cause it is if you have the flash emit a focus beam. It then needs to do that before you can shoot. This is something that should be turned off for outdoor situations.

You can always try a reset of the camera if that isn't the problem.

I did the two button reset and everything is back to normal.